Niklas Hietala, M.Sc., will defend the dissertation "Helical waves on quantized vortices" on 22 September 2017 at 12 noon in Aalto University School of Science, lecture hall K216, Otakaari 4, Espoo. In this dissertation, numerical simulations are used to study quantized vortices in superfluids. The helical waves of these line-like vortices play an important role in the superfluid turbulence.